SNR drops as weather gets warmer.

Anyone else noticed this. I am running my SNR target at 1.5db and when it gets cold it can rise to 2.5db, but as the weather has warmed up it has dropped to 1.1db, particularly today. Might have to force a resync unless the router does it itself.

Re: SNR drops as weather gets warmer.

Whens its cold the copper contracts and the line effectively becomes shorter i think.

When its hot the opposite happens and the line becomes longer ?

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Re: SNR drops as weather gets warmer.

Even if the change in length made a measurable change in attenuation then the change in diameter along that length would have the opposite effect. Shorten line >>> decrease attenuation. Reduce Diameter >>> increase resistance and thus attenuation!

Re: SNR drops as weather gets warmer.

Always thought this was due to physics, and the laws of thermodynamics. As Anonymous has said, if things are super cooled so they become super conducting, there is no electrical resistance, and because the atoms are hardly vibrating any more (due to heat), there's no 'quantum' fluctuations being generated in the material as noise, so the noise floor of the medium is reduced. If the material is hotter, there is more energy, and so more noise.

Re: SNR drops as weather gets warmer.

In typical UK temperatures - 0o to 20o c the difference is about 0.35% per degree C so for a 10o drop there will be a 3.5% reduction in resistance. But buried cables do not change temperature rapidly! The impedance of the line is not just resistive but complex especially at the higher frequencies. It may have a little effect but not one that significantly improves data rates.